Thin-film ferroelectric capacitors consisting of PbZr 0.53 Ti 0.47 O 3 sandwiched between La 0.5 Sr 0.5 CoO 3 electrodes have been deposited using pulsed laser deposition. The combination of oxidic perovskite-type materials results in capacitors with a coercive field (E c ) which is comparable with values for bulk ceramics. Textured thin-film capacitors with a columnar microstructure show lower switching voltages than epitaxial films. No thickness dependence of E c and a good endurance up to 10 11 cycles have been observed for epitaxial as well as textured capacitors with oxidic electrodes. In contrast, capacitors with a metallic top electrode show an increase of E c with decreasing thickness of the ferroelectric layer. We show that charge injection can explain the experimentally observed increase of E c with decreasing ferroelectric layer thickness. An overview is given of the growth conditions needed for PbZr 0.53 Ti 0.47 O 3 films, because the precise stoichiometry is of the utmost importance for the capacitor quality.
Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors Spijkman, M.; Smits, E. C. P.; Cillessen, J. F. M.; Biscarini, F.; Blom, P. W. M.; de Leeuw, D. M.
We present a model that describes grain-boundary-limited conduction in polycrystalline semiconductors, for thermally assisted ballistic as well as diffusive transport, both for degenerate and nondegenerate doping. In addition to bulk parameters ͑the carrier effective mass and mean free path͒ the model contains grain boundary parameters ͑barrier height and width͒ and a coefficient of current nonuniformity. Temperature-dependent conductivity and Hall measurements on polycrystalline SnO 2 thin films with different Sb concentrations are consistently interpreted.
We present a study of electrical characteristics of ferroelectric field-effect transistors made of PbZr0.2Ti0.8O3 and SnO2:Sb thin films. Due to properly chosen semiconductor parameters, the transistor channel can be totally depleted by the ferroelectric charge displacement. The observed remnant on/off ratio of the channel current amounts to 7×103. Pulse response measurements give information on data retention, device speed, and the occurrence of charge injection. The results lead to important design considerations for ferroelectric transistors.
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